A known art generates a reference voltage by smoothing a PWM (pulse width modulation) signal, determines the light amount of a laser diode (LD), and thus adjusts the LD power using the reference voltage.
According to the art, it is conceivable that, in usual use where a higher degree of accuracy in the LD power is required, the LD power is set at a maximum value and, in a case (such as in a toner save mode) where a lower power is required, the PWM (H/L) signal is used. However, with the art, in a case where a power higher than the power in the usual use is required, it is difficult to output the required power. Moreover, while the reference voltage is generated from the PWM signal, there is an error in the high level of the generated PWM signal. This is a potential cause of an undesired LD power.
Thus, there is a need for a device that is capable of switching the power in the usual use to a higher one than the power in the usual use while maintaining the accuracy in the usually used light output power.